大兴安岭加格达奇东北部花岗岩类形成时代、地球化学特征及成因

研究区位于大兴安岭兴安地块的东北部。本文主要讨论了碱长花岗岩和花岗斑岩两种岩石类型，并对其成岩年代、地球化学特征、成因及构造环境进行了深入讨论。研究结果显示：具有高SiO₂、A1₂O₃、TFeO/MgO，贫MgO、TiO₂、P₂O₅等特征；A/NK-A/CNK和w（K₂O）-w（SiO₂）图解显示，样品主要为过铝质、高钾钙碱性岩石。并且（Na₂O+K₂O）/CaO-w（Zr+Nb+Ce+Y）、TFeO/MgO-w（Zr+Nb+Ce+Y）图解和锆石饱和温度都显示，研究区花岗岩类岩石具有高分异Ⅰ型花岗岩的特征。锆石LA-ICP-MS U-Pb定年研究获得128~124 Ma的岩体侵位年龄，其形成的大地构造背景为蒙古-鄂霍茨克洋消亡之后，陆陆碰撞造山演化晚期地壳伸展背景，岩浆起源于壳内火成岩源岩的部分熔融。

Formation Age,Geochemical Characteristics and Genesis of Granites in Northeastern Jiagedaqi of Daxing'anling

The study area is located in the northeastern part of the Xing'an block in DaXing'anling. The main types of rocks focused on are alkali feldspar granite and granite porphyry, and their formation age, geochemical characteristics, genesis and tectonic setting were studied in depth. The results show that SiO₂ has a high mass fraction, with high A1₂O₃, TFeO/MgO, poor MgO, TiO₂, P₂O₅, etc.. A/NK-A/CNK and w(K₂O)-w(SiO₂) diagrams show that the samples are mainly of peraluminous, high potassium calc alkaline granites. All the (Na₂O+K₂O)/CaO-w(Zr+Nb+Ce+Y), TFeO/MgO-w(Zr+Nb+Ce+Y) and zircon saturation temperatures show that the rocks are of highly fractionated I-type granites. The emplacement age of the rock mass obtained from zircon LA-ICP-MS U-Pb dating is 128-124 Ma. It is concluded that the tectonic setting of the geotectonic background was the crustal extension in the late stage of continental collision orogeny after the extinction of the Mongolia-Okhotsk Ocean. The magma was originated from the partial melting of igneous source rocks.